There is a known photodiode array (semiconductor light detection element) having a plurality of avalanche photodiodes operating in Geiger mode, quenching resistors connected in series to the respective avalanche photodiodes, and signal lines to which the quenching resistors are connected in parallel (e.g., cf. Patent Literature 1). In this photodiode array, when an avalanche photodiode forming a pixel detects a photon to induce Geiger discharge, a pulsed signal is obtained by action of the quenching resistor connected to the avalanche photodiode. Each avalanche photodiode counts a photon. For this reason, with incidence of multiple photons at the same timing, we can also find out the number of incident photons in accordance with an output charge amount or signal intensity of all output pulses.